1. Field of the Invention
The present invention relates to an image vibration reduction device for reducing an image vibration of an object image in an optical apparatus such as a camera, a telescope and a video camera.
2. Related Background Art
An image vibration reduction device reduces a deflection of an optical axis with respect to a photographing screen by moving an image vibration reduction optical system incorporated as a whole or a part of a photographic optical system of an optical apparatus such as a camera, a telescope and a video camera, in such a direction as to offset a vibration of a camera shake caused by a photographer.
FIGS. 9 and 10 are explanatory views each showing a structure of a prior art image vibration reduction device incorporated into the camera.
In an example shown in FIG. 9, in an interior of a lens barrel unit L, a lens holder 122 for holding an image vibration reduction lens 121 and a lens frame 123 for supporting the lens holder 122 are so disposed as to be movable in two-dimensional directions, i.e., X- and Y-directions within the plane orthogonal to an optical axis. The lens frame 123 of an image vibration reduction optical system is supported by wires 136, 137, 138, 139 provided in parallel to the optical axis and composed of resilient members, which are fixed to four positions of the lens frame 123.
Upper and right sides of the lens frame 123 are formed with a coil support frame of a voice coil motor, and coils 124, 125 of the voice coil motor are fixed to the lens frame 123, thus constituting the voice coil motor. The lens frame 123 is driven by this voice coil motor, thereby moving the above-mentioned image vibration reduction optical system.
On the other hand, also in an example shown in FIG. 10, in the interior of the lens barrel unit L, a lens holder 152 for holding an image vibration reduction lens 151 is movable in two-dimensional directions, i.e., X- and Y-directions within the plane orthogonal to the optical axis. A Y-directional stage 153 and an X-directional stage 155 that constitute the image vibration reduction optical system are supported by guide portions 153-1a, 153-1b, 155-1a, 155-1b, shafts 153-2a, 153-2b, 155-2a, 155-2b, and coil springs 154-1a, 154-1b, 154-2a, 154-2b, 156-1a, 156-1b, 156-2a, 156-2b.
An upper side of the Y-directional stage 153 is formed with a coil support frame of a voice coil motor, and a coil 157 of the voice coil motor is fixed to the coil support frame of the voice coil motor, thus constituting the voice coil motor. Similarly, a left side of the X-directional stage 155 is formed with a coil support frame of the voice coil motor, and a coil 158 of the voice coil motor is fixed to the coil support frame of the voice coil motor, thus constituting the coil voice motor. The Y- and X-directional stages 153, 155 are driven by these voice coil motors, thereby moving the above-described image vibration reduction optical system.
By the way, if a centrobaric position of the movable portion moved by the voice coil motor, a portion where a load between a guide device and the movable portion is produced, and a portion where a driving force of the voice coil motor is produced, exist in positions spaced far from each other, it follows that a moment is caused with the movement. If this moment has a small value, there might be no problem. In the case of a large value, however, a problem may arise.
For example, in the image vibration reduction device having a structure illustrated in FIG. 9, when an image vibration reduction lens 121 is moved at a high speed, the wires 136, 137, 138, 139 are buckled and deformed due to the moment described above and therefore do not function as the resilient members.
Further, in the image vibration reduction device having a structure illustrated in FIG. 10, when the image vibration reduction lens 121 is moved at the high speed, the guide portions 153-1a, 153-1b, 155-1a, 155-1b and the shafts 153-2a, 153-2b, 155-2a, 155-2b are inclined and contact each other, with the result that relative motions between the guide portions and the shaft are hindered by frictions therebetween. Also, such an increase in the moment leads to an increment in terms of a frictional load between the guide portion and the shaft. As a result, a rise in electric power consumed is brought about.
Accordingly, under such circumstance, it is quite difficult to reduce the vibration by moving the image vibration reduction lens to a desired position, resulting in a such problem that the image vibration can not be reduced.